Build shared lib on windows?

[h-vetinari]

This recently came up in #213, where I noted:

I see [@isuruf] added the =NO on windows in 8059f3a (though I don't see relevant comments in the corresponding PR). That commit is also relevant because it introduced another point about this recipe I'm not 100% sure about - currently on windows, libllvm16 & llvm are completely empty packages - I presume because this would be for the shared libraries which we're not building currently.

I've also just stumbled across apache/arrow#37412, which does

  if(MSVC)
    # It seems that conda's llvmdev for Windows doesn't provide shared
    # library.
    set(ARROW_LLVM_USE_SHARED_DEFAULT OFF)
  else()
    set(ARROW_LLVM_USE_SHARED_DEFAULT ${ARROW_DEPENDENCY_USE_SHARED})

Would appreciate your input @isuruf on whether we should do this at all, and what blockers (if any) you see.

[isuruf]

AFAIK, upstream LLVM does not support shared libraries on windows.

[h-vetinari]

Indeed:

LLVM_BUILD_LLVM_DYLIB:BOOL:
[...] This option is not available on Windows.

[h-vetinari]

Upstream support is slowly materializing: llvm/llvm-project#109483